Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 24-27). Also available on the Internet.

Thesis (M.S.)--Northern Illinois University, 2002. / Includes bibliographical references.

Thesis (M.S.)--Eastern Illinois University, 1987. / Includes bibliographical references (leaves 27-28).

This thesis discusses the field of asymmetric synthesis of oxiranes. An introduction highlighting the most successful methods for the synthesis of chiral epoxides including the latest advances in these areas, with particular attention paid to the organocatalytic techniques is presented in chapter one. The second chapter begins by summarizing the group's previous efforts in the initial stage of this project and sets the motif for this work. These include: the synthesis of enantiopure dihyroisoquinolinium salts with a chiral residue attached to the exocyclic carbon-nitrogen bond as catalysts for asymmetric epoxidation; utilizing systems such as camphor and natural amino acids as starting points for these syntheses; developing other catalyst families in order to delve into the possibility of eliminating the structural weaknesses leading to loss of enantioselectivity in the oxygen transfer process; attempts to probe the reactive intermediates responsible for the asymmetric induction by analytical techniques; checking for catalyst applicability with different alkene and sulphide substrates; the development of anhydrous reaction conditions and their testing with the successful catalysts prepared. Enantiomeric excesses of up to 70% have been obtained. An attempt at exploring the synthesis of chiral reagents for the asymmetric epoxidation via a Payne/peroxyacid route is also described. This chapter concludes with a comparison of the catalyst families generated, and presents a few suggestions for future research in this area. The third chapter is dedicated to, the experimental section and includes the methods of synthesis and characterization of the compounds in the results and discussion chapter. There are three appendices at the. end of the thesis; Appendix A contains a summary the X-ray reports regarding the crystallographic data of the compound structures presented in chapter two. Appendix B contains samples of the analytical spectra of the enantiomeric excess determination for epoxides. Appendix C includes a copy of both publications I was involved in during my research in this topic.

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Cesium adsorption on Pt(111) and its coadsorption with iodine and oxygen is studied in this dissertation. The work function during Cs dosing first decreases and at Δφ≈ 3 eV ( Cs = 0:15) the surface undergoes surface transition between a disordered anomalous state (Pt(111)(anom)-Cs) and islands of a Pt(111)(2 x 2)-Cs causing a change in the slope of the work function curve. The work function curve reaches minimum at -5:5 eV where the surface is fully covered with the Pt(111)(2 2)-Cs structure (θCs = 0:25). Further Cs dosing results in a work function increase and the surface undergoes a phase transition to Pt(111)(p3 p3)-Cs. The Cs saturated structure (Pt(111)(ihcp)-Cs) has an hexagonal symmetry with the unit cell vector aligned with the h1; 0i direction of the substrate. Cs in the anomalous state desorbs from the surface in a high-temperature TDS peak (> 1000 K). When the lock-in TDS detection technique is used, this peak appears to be phase shifted by 180 when compared to the desorption peak of normally adsorbed Cs ( Cs > 0:15) . This phase shift is a consequence of a positive charge of desorbing Cs. The TDS and work function behavior were explained by a Monte Carlo desorption model incorporating di¤erent desorption behavior for all four observed adsorption phases. When O2 is dosed on a Pt(111)-Cs surface, the maximum coverage of oxygen bonded to the surface is significantly increased in comparison to Pt(111). Anomalously adsorbed Cs activates the O2 bond but does not interact strongly with coadsorbed O. However, when O2 is dosed on Pt(111)(ihcp)-Cs, the oxygen first adsorbs to a sub-layer adsorption site and strongly interacts with Cs. The oxygen in this state is responsible for thermal stabilization of coadsorbed Cs. When iodine is coadsorbed on a Pt(111)-Cs surface, it also strongly interacts with and thermally stabilizes Cs. During the desorption of Cs,I layers, some Cs and I desorb together in the form of a CsxIy cluster. The surface structures observed by LEED during the coadsorption of Cs and I are in good agreement with atomic arrangements predicted for ionic layers. The validity of this conclusion and the general behavior of ionic layers was checked by an electrostatic energy calculation for various structures. / Graduate / 0494 / 0748

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No description available.

The compounds in the series from triphenylphosphine to triphenylbismuthine were examined as acceptors in oxygen transfer reactions involving the l-pyrroline-l-oxides. Triphenylphosphine was found to offer a useful route from the l-pyrroline-l-oxides to the corresponding pyrrolines. The second part of this work is centred on the structural investigation of Sanno's base (XV) (l), obtained as a by-product in the reductive cyclization of ethyl 2-acetyl-2-ethyl-4-methyl-3-nitromethyl valerate (aγ -nitro-ketone) and formulated by the author as having the Δ’ -pyrroline structure; this compound has since been found to be a cyclic nitrone (XVI). In the case of this complex nitrone, the oxygen transfer reaction to triphenylphosphine has been successful, yielding two isomeric Δ' -pyrrolines. The isolation of a Δ -pyrroline structure is confirmation of the proposed cyclic nitrone (XVI) structure for Sanno's base and as this provides a practical application of this reaction in structural work as well as showing that triphenylphosphine will reduce N-oxides in the presence of an ester group. / Science, Faculty of / Chemistry, Department of / Graduate

Dissolved oxygen was studied in distilled water and salt solutions by means of nuclear magnetic resonance. The free induction technique was employed to measure the spin lattice relaxation time, T-^, for oxygen-free distilled water and for water containing oxygen under one atmosphere of air and one atmosphere of oxygen at temperatures of 1° to 75°C. The same measurements were made for solutions of 0.5 M sodium chloride at temperatures of 1° to 40°C. The spin lattice relaxation probability, 1/T[subscript 1(c)], in the presence of paramagnetic oxygen, was attributed to two relaxation mechanisms: the first a dipole-dipole interaction and the second a hyperfine interaction. The two terms were evaluated from measurements of T[subscript 1(c)] at two different magnetic field strengths at 20°C. Using the theoretical relationship between the dipole-dipole term and η/T, the results were used to evaluate the hyperfine term at different temperatures. The activation energy obtained from the variation of the dipole-dipole term with temperature was assumed to represent the energy required to break one hydrogen bond between two water molecules. The activation energy found for the hyperfine term was taken as a measure of the breaking of a hydrogen bond between one oxygen molecule and an aggregate of water molecules. The activation energy of the hyperfine term was found to be a function of temperature. Comparison of this quantity with heats of solution of dissolved oxygen in distilled water and salt solution showed a similar pattern of change in both. Oxygen supersaturation was studied in sea water cultures of Nitzschia closterium and Chlorella strain "A" at a temperature of 12°C. Saturation values up to 200% were reached under illumination with light energy of 9.2x10[power -3] langlies/min. Nitzschia was found to be more photosynthetically active, under the same culture conditions, than Chlorella. Oxygen production by Nitzschia was shown to be a function of the difference in photosynthetic pigment concentrations (chlorophyll-a — non-astacin carotenoid), total alkalinity, and the change in catalytic activity of the medium. Variation of oxygen concentration in Nitzschia cultures under light and dark periods indicated a mechanism by which oxygen may escape as microbubbles to the atmosphere. The rate of oxygen desupersaturation was measured in water free of organisms. The rate increased with increase of ion content and with the surface to volume ratio of the water column, but was not influenced by addition of siliceous particulate matter to the supersaturated water. Small addition of a surface active agent (heptanoic acid) increased the oxygen desupersaturation rate but further addition decreased the rate. / Science, Faculty of / Chemistry, Department of / Graduate